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Search: id:A016838
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| 9, 49, 121, 225, 361, 529, 729, 961, 1225, 1521, 1849, 2209, 2601, 3025, 3481, 3969, 4489, 5041, 5625, 6241, 6889, 7569, 8281, 9025, 9801, 10609, 11449, 12321, 13225, 14161, 15129, 16129, 17161, 18225
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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If Y is a fixed 2-subset of a (4n+1)-set X then a(n-1) is the number of 3-subsets of X intersecting Y. - Milan R. Janjic (agnus(AT)blic.net), Oct 21 2007
A bisection of A016754. Sequence arises from reading the line from 9, in the direction 9, 49,... in the square spiral whose vertices are the squares A000290. - Omar E. Pol (info(AT)polprimos.com), May 24 2008
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LINKS
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Milan Janjic, Two Enumerative Functions
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CROSSREFS
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Cf. A000290, A001539, A016742, A016754, A016802, A016814, A016826.
Sequence in context: A039940 A012111 A138998 this_sequence A087691 A014730 A164343
Adjacent sequences: A016835 A016836 A016837 this_sequence A016839 A016840 A016841
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KEYWORD
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nonn,easy
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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